A unidirectional dynamic microphone is preferably adopted particularly in a handheld vocal microphone, and, as illustrated in FIG. 7A and FIG. 7B, there is known a method of covering a dynamic microphone unit 1 with a cylindrical tube 2 made of an acoustic resistance material as one method for enhancing sensitivity to sound pressures (refer to Japanese Unexamined Utility Model Application Publication No. H06-48295 as a similar example).
FIG. 8A illustrates a polar pattern of the dynamic microphone unit 1 covered with the cylindrical tube 2, and FIG. 8B illustrates a frequency response characterized thereof. In contrast, FIG. 9A illustrates a polar pattern of the dynamic microphone unit 1 not covered with the cylindrical tube 2, and FIG. 9B illustrates a frequency response characteristic thereof.
In a case of being covered with the cylindrical tube 2, the sensitivity to the sound pressures is higher by approximately 4 dB as compared to a case of being not covered with the cylindrical tube 2, but as understood from a contrast between FIG. 8A, FIG. 8B, FIG. 9A, and FIG. 9B, there occurs a problem that the directionality and frequency response degrade.